Attention-deficit/hyperactivity disorder (ADHD) is a pervasive developmental disorder reported to affect between 2-20% of children. The disorder is characterised by inappropriate levels of inattentiveness, impulsivity, and hyperactivity. Genetic and electrophysiological studies have suggested dysfunction in dopamine-mediated frontal and norepinephrine-mediated parietal attentional systems. The mainstream treatment for ADHD has been stimulant medication, which blocks the reuptake of Dopamine. Stimulants have short-term benefits for around 60% of children with ADHD, however, long-term benefits have not been demonstrated, and adverse side effects are often intolerable. Since the 1970s, Neurotherapy (EEG-Biofeedback) has shown promise as a safe treatment for children with ADHD. Several recent controlled studies have compared Neurotherapy with stimulant medication, and found Neurotherapy to be as effective as stimulants in redressing symptoms in around 70%-80% of children with ADHD, without adverse side effects. The purpose of this thesis was to investigate changes in the brain electrical activity of seventeen boys with ADHD aged 7-15 years (mean 10.35), before, and after Neurotherapy Treatment. The dependent variables were pre- and post-Neurotherapy changes in: (a) Steady-state Visually Evoked Potentials (SSVEP), while performing the CPT-AX version of the continuous performance task; (b) behavioural measures of attention, derived from analysis of key-presses during the CPT-AX task; (c) parent and teacher reports of DSM-IV ADHD symptoms, as assessed by the Australian Twin Behaviour Rating Scale (ATBRS); and (d) performance on a Continuous Performance Task, the Test of Variables of Attention (TOVA). Following Neurotherapy, changes in the amplitude and latency of the steadystate visually evoked potential (SSVEP) indicated that the functioning of medial frontal, right pre-frontal, and right parietal regions significantly improved, suggesting increased activation and speed of neural processing. These changes in brain electrical activity were associated with normalisation of TOVA scores and DSM-IV ADHD symptoms. This research is the first to demonstrate that Neurotherapy resulted in the dynamic neuromodulation of the dopamine-mediated frontal and norepinephrinemediated parietal components of the attentional system, as proposed by Tucker and Williamson’s (1984) model of the attentional system. It provides further support to the recent controlled studies and metaanalysis that suggest that Neurotherapy is an effective and efficacious treatment for ADHD. Given that, treatment effects are expected to be permanent and devoid of adverse side effects, Neurotherapy should be considered as the primary treatment for ADHD. Further research should focus on how to improve Neurotherapy protocols and service delivery for ADHD and other brain based disorders.